external-lib-deps --missing could suggest installing MDX for MDX stanzas

craigfe commented 4 years ago

When attempting dune build in a repository using MDX stanzas (with no external libraries initially available), the user gets an experience like the following:

run dune build;
fail due to libraries not available. run dune external-lib-deps --missing @@default;
run the suggested opam install ... command;
run dune build again;
fail due to missing mdx dependency for the MDX stanza, with a nice error message:

File "tests/dune", line 1, characters 0-45:
1 | (mdx
2 |  (files run.t)
3 |  (packages foo))
Error: Program ocaml-mdx not found in the tree or in PATH
 (context: default)
Hint: opam install mdx

This could be improved slightly by considering mdx as part of dune external-lib-deps @@foo if @foo will trigger an MDX stanza.

craigfe commented 4 years ago

CC: @NathanReb.

emillon commented 2 years ago

I think that this one should be closed now that external-lib-deps is not a dune feature anymore.

ocaml / dune

external-lib-deps --missing could suggest installing MDX for MDX stanzas #3454